(1) Field of the Invention
This invention relates to a method for detecting and measuring the amount of cholesterol which is deposited in the bodies of mammals.
(2) Description of the Prior Art
In the conventional art, there has been proposed no appropriate method for detecting directly or locally the cholesterol which is deposited in a living body, especially in the intima of artery of human body. For example, in the case of human body, it is difficult to determine the state of deposition of cholesterol by cytohystologic diagnosis in which an artery is cut open and the inside wall is subjected to macroscopic observation.
The state of deposition of cholesterol in the artery of human body was hitherto determined by injecting a contrast medium into an artery, taking an X-ray photograph and then observing the shadows on the obtained photograph. In another method, the determination of lipid (cholesterol) in serum was adopted. The result to this method, however, indicates the state of whole human body or considerably large part of the body, and the state of any specific part cannot be determined.
In the determination of cholesterol in blood, cholesterol is oxidized by an enzyme and generated peroxide and dye-precursor are subjected to oxidation-coupling in the presence of an enzyme, and then the quantity of developed dye is determined by absorptiometric analysis. It is difficult to determine the cholesterol deposited in a living body, especially in arteries, by means of the method utilizing chemical reaction like this.
It is said that arteriosclerosis, especially atherosclerosis of human as well as other mammals is caused by the deposition in the intima of cholesterol contained in blood. Thus, for the purpose of preventing or treating the atherosclerosis, a medicine having an effect to reduce the cholesterol value in the serum of human is administered.
The substance which causes atherosclerosis in human body by depositing in intima is a kind of of lipids which are produced in living bodies. At least the vertebrate animals, especially mammals, are concerned, such chemical compounds are known generally as cholesterol because the fundamental skeletal structures of them are the same.
There is hitherto known a method for the diagnosis of arteriosclerosis by administering a hematoporphyrin derivative to rabbits. A typical hematoporphyrin is exemplified by PHOTOFRIN II (trademark supplied by Photofrin Medical Inc.) This example is desribed in the following reference:
V. Neave et al., NEUROSURGERY, vol. 23, pp 307-312
However, it was found by the inventors of the present invention that the generation of fluorescence is weak when the foregoing Photofrin II is used for the method of the present invention. In the case that the generated fluorescence is weak, the determination of cholesterol is difficult because the cholesterol is determined by measuring the generated fluorescence in the method of the present invention.
Incidentally, the compounds themselves used in the method of the present invention are already known as diagnostic and therapeutic agents for cancer which are described in European Laid-Open Patent Publication Nos. 168831, published Jan. 22, 1986, equivalent to U.S. Pat. No. 4,693,885, issued Sept. 15, 1987;--; 168832, published Jan. 22, 1986, equivalent to U.S. Pat. No. 4,675,338, issued June 23, 1987;--; 200218, published Nov. 5, 1986, equivalent to U.S. Pat. No. 4,656,186, issued Apr. 7, 1987;--; 210351, published Feb. 4, 1987 and 213272, published Mar. 11, 1987. It should be noted that the field of art in the present invention is of course different from the field of art in the diagnosis and therapy of cancer.